Use mixlib::config strict mode when parsing gitlab.rb
Fixes: #2745 (closed)
Only turn strict mode on when parsing the gitlab.rb. Strict mode will throw an error for anything not found in mixlib::config's special config syntax (which we don't use). This change also patches that behaviour so we don't get the error if the change is in the config map configuration
property. (Which is where our attributes end up defined)
Edited by GitLab Release Tools Bot